Zinc-Flake Dip-Spin Coating
Electroplating & electroless plating · Dip / immersion
Zinc-flake is a non-electrolytic zinc/aluminum-flake basecoat, often with a topcoat, for fasteners and high-strength steel.
What is Zinc flake?
It includes generic systems in the Dacromet-, Geomet-, and Delta-Protekt class without using those brands as the specification.
How it works
Clean parts are dipped in a water- or solvent-borne dispersion of zinc and aluminum flakes, spun to remove excess, then cured. Two or more basecoat cycles build a lamellar barrier and sacrificial zinc network; a topcoat controls friction, color, and chemical resistance. Because no electrolytic deposition or acid pickling is inherently required, the process greatly reduces hydrogen-embrittlement risk. Dip-spin drainage can still fill recesses and create head or thread buildup.
Why specify it
- Common systems target 600–1000 h to red rust
- Typical 6–15 µm total coating
- No electrolytic hydrogen charging
- Topcoats can control fastener friction
Where it falls short
- Dip-spin buildup can clog small recesses
- Contact points and recesses may show coverage variation
- Cure temperature can affect heat-treated parts
- Brand and grade are not interchangeable without qualification
Zinc flake at a glance
Zinc flake is strongest on corrosion protection (85 of 100), at a premium cost. Surface hardness is not rated: the finish leaves the part's own surface.
Each score is 0–100 against every finish in this catalog. Corrosion comes from salt-spray life (ASTM B117, log scale) and hardness from the finish layer's Vickers or pencil hardness; cosmetic, lubricity and cost are FabDigit's engineering assessment. Economy on the radar is the inverse of cost.
Zinc flake key numbers
Typical values from the governing specifications and shop practice; bars are this finish against the highest value among electroplating & electroless plating finishes.
- Thickness
- 8–12 µm total for multi-coat basecoat plus topcoat fastener systems
- Corrosion (salt spray)
- 600–1,000 h per ASTM B117 per selected ASTM F1136 or ISO 10683 system — Typical red-rust range for qualified multi-coat systems; exact grade controls.
- Electrical
- Insulating
- Colours
- silver gray
- black
- Appearance
- Matte silver-gray or black, with visible dip-spin contact variation acceptable for functional fasteners.
Specifications for Zinc flake
The documents a drawing cites to define this finish, with the Type / Class rows that apply. Each links to a page explaining the standard.
| Standard | Type / Class | Thickness | Requirement / test | Status |
|---|---|---|---|---|
Standard Specification for Zinc/Aluminum Corrosion Protective Coatings for Fasteners · ASTM | Grade 1 | 4–5 µm | Basecoat only. · 16–20 g/m² average. · 240 h salt spray for chromium-containing system. | Withdrawn |
| Grade 2 | 5–8 µm | Heavier basecoat only. · 20–28 g/m² average. · 500 h C or 240 h NC salt spray. | ||
| Grade 3 | 6–12 µm | Basecoat plus clear sealer. · 22–34 g/m² average. · 1000 h C or 720 h NC salt spray. | ||
| Grade 4 | 8–15 µm | Heavy basecoat only. · 28–50 g/m² average. · 1000 h C or 500 h NC salt spray. | ||
| Grade 5 | 6–12 µm | Basecoat plus lubricated sealer. · 22–34 g/m² average. · 1000 h C or 720 h NC salt spray. | ||
| Grade 6 | 8–15 µm | Basecoat plus pigmented topcoat. · 23–40 g/m² average. · 500 h C or 500 h NC salt spray. | ||
Fasteners — Non-Electrolytically Applied Zinc Flake Coating Systems · ISO · alternative | 240 h reference | ≥ 4 µm | Minimum neutral-salt-spray duration; reference system thickness only. · ISO 9227 NSS; corrosion performance governs. | Active |
| 480 h reference | ≥ 5 µm | Minimum neutral-salt-spray duration; reference system thickness only. · ISO 9227 NSS; corrosion performance governs. | ||
| 600 h reference | ≥ 6 µm | Minimum neutral-salt-spray duration; reference system thickness only. · ISO 9227 NSS; corrosion performance governs. | ||
| 720 h reference | ≥ 8 µm | Minimum neutral-salt-spray duration; reference system thickness only. · ISO 9227 NSS; corrosion performance governs. | ||
| 960 h reference | ≥ 10 µm | Minimum neutral-salt-spray duration; reference system thickness only. · ISO 9227 NSS; corrosion performance governs. |
Test and related methods: ASTM B117 (Standard Practice for Operating Salt Spray (Fog) Apparatus).
Drawing call-out
ZINC-FLAKE COATING PER ISO 10683, 8 µm MIN, SILVER, INTEGRAL LUBRICATED TOPCOAT; 720 H MIN TO RED RUST PER ASTM B117; COEFFICIENT OF FRICTION 0.10–0.16Pattern: ZINC/ALUMINUM FLAKE COATING PER LEGACY ASTM F1136, GRADE <1–6>, <C|NC>, <COLOR>, <FRICTION>; USE ASTM F3393 FOR NEW DESIGN
Which materials take Zinc flake?
Verdict per material family, with the grades that behave differently. Each family links to its datasheets in the material library.
| Material family | Verdict | Notes |
|---|---|---|
| Yes | Primary use, especially high-strength fasteners.
| |
| Limited | Only steel AM fasteners or small parts that can tolerate dip-spin and the cure cycle. | |
| Limited | Sacrificial zinc is generally unnecessary and can create galvanic concerns. | |
| No | Zinc-flake fastener systems are for steel; aluminum uses conversion or anodize. | |
| No | Not a brass finish. | |
| No | Not a copper-alloy finish. | |
| No | Fused-filament polymers are incompatible with this process. | |
| No | Not specified for magnesium. | |
| No | Polymer powder-bed prints are incompatible with this process. | |
| No | Organic polymers cannot take this inorganic metal-finishing process. | |
| No | Photopolymer prints are incompatible with this process. | |
| No | Polymer powder-bed prints are incompatible with this process. | |
| No | Not a titanium finish. | |
| No | Intended for steel fasteners, not zinc die castings. |
How Zinc flake is applied, and what it does to the part
- 1Alkaline clean or blast
- 2Dip basecoat
- 3Spin
- 4Cure
- 5Repeat basecoat if required
- 6Apply topcoat
- 7Final cure
- 8Test corrosion and friction
| Dimensions | Validate 6–15 µm total buildup with thread gauges and coefficient-of-friction testing on production fasteners. |
|---|---|
| Build-up per side | 6–15 µm — Dip-spin removes bulk excess, but thread roots and recessed heads can retain extra coating. |
| Masking | Usually needed. Mask electrical grounds, weld zones, precision seats, and recesses that cannot drain. |
| Electrical | Insulating |
| Temperature limit | 180 °C (356 °F) continuous |
| Appearance | Matte silver-gray or black, with visible dip-spin contact variation acceptable for functional fasteners. |
| Added lead time | 4–8 working days on top of the bare part |
Design rules for Zinc flake
What to decide on the drawing before the part goes to the finisher.
- Specify system grade, not a brand alone.Basecoat, topcoat, thickness, and cure define performance.
- State friction range for fasteners.Topcoat controls clamp load at a given torque.
- Gauge threads after coating.Dip-spin liquid can accumulate in roots and recesses.
- Check cure temperature against the part.Some hardened or adhesive-containing assemblies cannot tolerate the cycle.
Zinc flake versus the alternatives
Finishes engineers weigh against Zinc flake, and when each wins.
| Finish | Corrosion | Hardness | Cosmetic | Cost | Thickness | Choose it when |
|---|---|---|---|---|---|---|
Zinc flake this page | 85 | — | 35 | $$$ | 6–15 µm | — |
| 86 | 60 | 48 | $$ | 5–15 µm | when a thin metallic electrodeposit and automotive-qualified finish are preferred | |
| 90 | 42 | 32 | $$ | 45–100 µm | when thick outdoor protection on structural steel is acceptable |
The radar overlays Zinc flake with Zinc-Nickel Plating, its most common alternative — chosen when a thin metallic electrodeposit and automotive-qualified finish are preferred. Scores in the table are 0–100 across every finish in the catalog.
Cost, lead time and compliance
Relative cost
Zinc-Flake Dip-Spin Coating is a premium-cost finish ($$$): cheaper than about 52 % of the finishes FabDigit quotes.
Finishing is priced per part with a lot minimum, from FabDigit's own China-side rates. The exact figure appears on the instant quote once the part is uploaded.
Lead time and compliance
| Added lead time | 4–8 working days |
|---|---|
| RoHS | Compliant |
| Notes | Modern Cr(VI)-free systems are available; legacy Dacromet-class formulations may use hexavalent chromium and must not be assumed compliant. |
What Zinc flake is used for
- High-strength fasteners
- Brake hardware
- Chassis bolts
- Spring steel clips
Zinc flake — frequently asked
zinc flake vs zinc nickel plating
Zinc flake is non-electrolytic, commonly 6–15 µm, and avoids plating-related hydrogen charging. Zinc-nickel is an electrodeposited 12–15% Ni alloy with better metallic continuity but still needs embrittlement controls.
does zinc flake coating cause hydrogen embrittlement
The coating step does not electrolytically generate hydrogen, which is why it is favored for high-strength fasteners. Pretreatment must also avoid uncontrolled acid pickling or include appropriate safeguards.
how thick is zinc flake coating
Qualified dip-spin systems are commonly 6–15 µm total, with 8–12 µm typical. Thread roots and recessed heads can retain more material, so gauge production parts.
Dacromet vs Geomet vs Delta Protekt
These names identify commercial zinc-flake system families, not one interchangeable finish. Specify ASTM F1136 or ISO 10683 performance, thickness, topcoat, color, friction, and salt-spray requirement.
how many salt spray hours for zinc flake
Many multi-coat fastener systems target 600–1000 h to red rust in ASTM B117. The valid acceptance value is the selected ASTM F1136 or ISO 10683 grade and qualified supplier system.
Other electroplating & electroless plating finishes
Black Nickel PlatingBlack nickel is a thin dark decorative electrodeposit, commonly applied over nickel, copper, brass, or zinc.CorrosionHardnessCost$$$
Brass PlatingBrass plating co-deposits copper and zinc to give steel, zinc die castings, or copper alloys a yellow decorative surface.CorrosionHardnessCost$$$
Bronze PlatingBronze plating deposits a copper-tin or related copper alloy for warm decorative color, antiquing, or selected functional bearing surfaces.CorrosionHardnessCost$$$
Cadmium PlatingCadmium is a sacrificial, lubricious coating retained mainly for aerospace, defense, and legacy hardware.CorrosionHardnessCost$$$$
Copper PlatingCopper plating is a conductive, ductile undercoat used for leveling, adhesion, shielding, and build-up.CorrosionHardnessCost$$
Decorative Nickel-Chrome PlatingDecorative chrome is a multilayer system: copper when needed, one or more nickel layers, and a very thin chromium topcoat.CorrosionHardnessCost$$$
Electroless Copper PlatingElectroless copper chemically deposits a conductive seed layer on catalyzed plastics and inside printed-circuit through-holes.CorrosionHardnessCost$$$
Electroless Nickel PlatingElectroless nickel is an autocatalytic nickel-phosphorus coating with nearly uniform thickness on complex geometry.CorrosionHardnessCost$$$Compare every electroplating & electroless plating finish side by side →